AP Chemistry : Special Groups

Study concepts, example questions & explanations for AP Chemistry

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Example Questions

Example Question #1 : Special Groups

Why are atomic halogens relatively reactive?

Possible Answers:

Halogens are monovalent anions, so they are very reactive

The valence shell of halogens has diradical character

Halogens have an unpaired electron in their valence shell and they only need one more electron to obtain an octet

None of the available answers

Gaseous halogens are very stable

Correct answer:

Halogens have an unpaired electron in their valence shell and they only need one more electron to obtain an octet

Explanation:

Halogens have seven electrons in their valence shell, so they only need one more electron to obtain a completely filled valence shell. In addition, the unpaired electron in the seven electron shell is a radical which is highly reactive.

Example Question #2 : Special Groups

Which of the following is not a property of the noble gases?

Possible Answers:

Noble gases have weak interatomic forces

Noble gases have low boiling points

Noble gases have low melting points

All noble gases are monoatomic under standard conditions

Noble gases are stable because of their complete octet, so they cannot take place in any reaction

Correct answer:

Noble gases are stable because of their complete octet, so they cannot take place in any reaction

Explanation:

While noble gases are very stable due to their filled octet, they actually do take place in certain reactions, so that is not a property of noble gases. All other answer choices are true.

Example Question #3 : Special Groups

Refer to Figure 1 for questions 1-6.

Below are the data for ionization energies of three elements X, Y, and Z. These elements are on the third peroid of the periodic table. The first four ionization energies for elements X, Y, and Z are given below in values of kJ/mol.

Figure 1: Ionization energies in kJ/mol for selected elements.

Which of the unknown elements would you expect to share chemical properties with strontium (Sr)?

Possible Answers:

Y and Z

X and Y

Z

X

Y

Correct answer:

Z

Explanation:

We know that element Z is magnesium due to its jump bwtween ionization energies 2 and 3. Magnesium is in the second group of the periodic table and shares similar chemical properties with other alkali earth metals, such as strontium.

Example Question #4 : Special Groups

The periodic table of elements is organized in order of atomic number, whic describes how many protons are found in the atom's nucleus. The position of the element in the periodic table can also yield insight into how that atom will respond to other atoms and how it will participate in a chemical reaction.

Sodium is found in the alkali metal group on the periodic table. What type of ion would you expect sodium to form in order to achieve a stable octet?

Possible Answers:

A cation, with a charge of -1

An anion, with a charge of -1

An anion, with a charge of +1

A cation, with a neutral charge

A cation, with a charge of +1

Correct answer:

A cation, with a charge of +1

Explanation:

Sodium is an alkali metal. All alkali metals are found in group 1 on the periodic table, and lose 1 electron in order to achieve a stable octet. Any ion that loses an electron, and thus becomes positively charged, is referred to as a cation. Anions are negatively charged ions, so sodium is not going to become an anion.

 

 

Example Question #5 : Special Groups

Below are the data for ionization energies of three elements X, Y, and Z. These elements are on the third peroid of the periodic table. The first four ionization energies for elements X, Y, and Z are given below in values of kJ/mol.

Figure 1: Ionization energies in kJ/mol for selected elements.

Which element(s) react(s) violently with water?

Possible Answers:

X and Y

Y and Z

Y

Z

X

Correct answer:

X

Explanation:

We know element X is sodium due to its discrepancy between IE1 and IE2. Sodium has one valence electron and is an alkali metal. Pure alkali metals react violently with water. The heavier the metal, the bigger the explosion. 

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